Genetic manipulation is a developing tool in cardiovascular research, and much of this work is done in mice. Ultrasound equipment designed for use on humans is not suitable for non-invasive monitoring of cardiovascular parameters in mice due to small organ size (5 mm dia heart) and high heart rates (400-600 bpm). We propose to develop an instrument to measure cardiac output and myocardial function non-invasively in mice and other small animals. The goal is to achieve measurements resolutions on the order of l ms in time, 0.1 mm in cardiac dimensions, and l cm/s in blood flow velocity. A miniature high frequency (20 MHz) ultrasonic transducer and pulsed Doppler instrumentation will be designed to measure aortic blood flow velocity and a high resolution M-mode echocardiograph (at 20 MHz) will be designed to measure cardiac dimensions and motion. The ultrasonic transmitter-receiver portions of the Doppler/M-mode and real time digital signal processing hardware will be interfaced with a personal computer for display and analysis. The system will be validated using static phantoms and tested on mice. In Phase II we will integrate these parts into a versatile computer-based ultrasonic measurement and analysis system for small animals ranging from mice to rabbits.